In general, when diesel fuel is burned in an engine, nitrogen oxides are produced in the exhaust gas. An exhaust gas recirculation (EGR) cooler provides a cooled dilutent to lower combustion temperatures and reduce the concentration of nitrogen oxides in the exhaust gases. Typically, when an engine is first started, an EBV assembly, separate from the EGR cooler, is used to bypass the EGR cooler and redirect uncooled gasses through the engine to accelerate engine warmup. These EBV assemblies must withstand high temperature and are typically complicated, with an expensive, machined housing.
With reference to FIG. 1, a conventional EBV assembly, generally indicated at 10, includes the conventional pair of butterfly valves 14, 14′ disposed on a common shaft 15. A conventional motor-driven, general purpose actuator (not shown), is provided to control operation of the butterfly valves 14, 14′ to open and close a bypass passageway 18. Thus, since two valves and two sealing surfaces are required, the EBV assembly 10 is large and costly.
Thus, there is a need to provide a compact, replaceable and cost-effective EBV.